Added utility class for managing SWT graphics context state more easily.

refs 2589

org.fortiss.tooling.base.ui/trunk/src/org/fortiss/tooling/base/ui/utils/GCUtils.java

+/*--------------------------------------------------------------------------+
+$Id: codetemplates.xml 1 2011-01-01 00:00:01Z hoelzl $
+|                                                                          |
+| Copyright 2016 fortiss GmbH                     |
+|                                                                          |
+| Licensed under the Apache License, Version 2.0 (the "License");          |
+| you may not use this file except in compliance with the License.         |
+| You may obtain a copy of the License at                                  |
+|                                                                          |
+|    http://www.apache.org/licenses/LICENSE-2.0                            |
+|                                                                          |
+| Unless required by applicable law or agreed to in writing, software      |
+| distributed under the License is distributed on an "AS IS" BASIS,        |
+| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
+| See the License for the specific language governing permissions and      |
+| limitations under the License.                                           |
++--------------------------------------------------------------------------*/
+package org.fortiss.tooling.base.ui.utils;
+
+import java.util.Deque;
+import java.util.LinkedList;
+
+import org.eclipse.swt.graphics.Color;
+import org.eclipse.swt.graphics.Font;
+import org.eclipse.swt.graphics.FontData;
+import org.eclipse.swt.graphics.GC;
+import org.eclipse.swt.graphics.RGB;
+import org.eclipse.swt.widgets.Display;
+
+/**
+ * Utility class for handling of {@link GC SWT graphics context} state and data.
+ * <P>
+ * Currently, this class only encapsulates the {@link GCStateManager} class, which can be used to
+ * store and restore attributes of the graphics context.
+ * 
+ * @author hoelzl
+ * @author $Author: hoelzl $
+ * @version $Rev: 18709 $
+ * @ConQAT.Rating YELLOW Hash: A85DD64B7EDBBAD1E1E3E8699FF2B4AD
+ */
+public final class GCUtils {
+
+	/** Creates the state manager for the given graphics context. */
+	public static GCUtils.GCStateManager createGraphicsContextManager(GC gc) {
+		return new GCUtils.GCStateManager(gc);
+	}
+
+	/**
+	 * Utility class managing SWT graphics context state by storing and restoring state attributes
+	 * of the underlying graphics context using the provided public methods.
+	 * <P>
+	 * Note that it is the obligation of the user of this class to ensure that methods are called in
+	 * order of the stack principle. Otherwise, {@link ClassCastException}s will occur.
+	 */
+	public static final class GCStateManager {
+		/** The graphics context to be managed. */
+		private final GC gc;
+		/** The stack used to store the current gc state attributes. */
+		private final Deque<Object> state = new LinkedList<Object>();
+
+		/** Constructor. */
+		public GCStateManager(GC gc) {
+			this.gc = gc;
+		}
+
+		/** Returns the graphics context. */
+		public GC GC() {
+			return gc;
+		}
+
+		/** Stores the alpha value. */
+		public GCStateManager alphaStoreAndSet(int alpha) {
+			state.push(new Integer(gc.getAlpha()));
+			gc.setAlpha(alpha);
+			return this;
+		}
+
+		/** Restores the alpha value. */
+		public GCStateManager alphaRestore() {
+			gc.setAlpha((Integer)state.pop());
+			return this;
+		}
+
+		/** Stores the current foreground color and creates and activates the given color. */
+		public GCStateManager foregroundStoreAndCreate(RGB rgb) {
+			state.push(gc.getForeground());
+			gc.setForeground(new Color(Display.getCurrent(), rgb));
+			return this;
+		}
+
+		/** Restores the previous foreground color and disposes the current one. */
+		public GCStateManager foregroundRestoreAndDispose() {
+			gc.getForeground().dispose();
+			gc.setForeground((Color)state.pop());
+			return this;
+		}
+
+		/** Stores the current background color and creates and activates the given color. */
+		public GCStateManager backgroundStoreAndCreate(RGB rgb) {
+			state.push(gc.getBackground());
+			gc.setBackground(new Color(Display.getCurrent(), rgb));
+			return this;
+		}
+
+		/** Restores the previous background color and disposes the current one. */
+		public GCStateManager backgroundRestoreAndDispose() {
+			gc.getBackground().dispose();
+			gc.setBackground((Color)state.pop());
+			return this;
+		}
+
+		/** Stores the current font and creates and activates the given font. */
+		public GCStateManager fontStoreAndCreate(FontData fontData) {
+			state.push(gc.getFont());
+			gc.setFont(new Font(Display.getCurrent(), fontData));
+			return this;
+		}
+
+		/** Restores the previous font and disposes the current one. */
+		public GCStateManager fontRestoreAndDispose() {
+			gc.getFont().dispose();
+			gc.setFont((Font)state.pop());
+			return this;
+		}
+	}
+}